The present invention relates to an internal combustion engine for a vehicle which has a cylinder block, a crank shaft and a plurality of pistons.
More particularly, the present invention relates to improvements in a sealing means between the cylinder block and the crank shaft in the internal combustion engine.
A conventional sealing means, located between a crank shaft and an oil seal case, is disclosed in Japanese Utility Model Laid Open No. Showa 55-168713. The oil seal case is secured to both a cylinder block and a crank shaft cap. The crank shaft includes a main journal and a flange shaft. The main journal is surrounded by a front main bearing insert and the flange shaft projects forwardly from the main journal. An outer diameter of the flange shaft of the crank shaft is larger than an outer diameter of the main journal and the flange shaft has the same shaft axis as the main journal. A peripheral portion of the flange shaft of the crank shaft is positioned forwardly and apart from both the cylinder block and the crank shaft cap. Therefore, even when the crank shaft receives a thrust load, the peripheral portion of the flange shaft does not contact the cylinder block or the crank shaft cap.
The oil seal case is secured to both the cylinder block and the crank shaft cap. The oil seal case has a larger inner diameter than the outer diameter of the flange shaft. An outer peripheral surface of the flange shaft is spaced from an inner surface of the oil seal case.
The seal means has a "C" cross-sectional shape and inner and outer portions of the seal means contact the outer peripheral surface of the flange shaft and the inner surface of the oil seal case, respectively. The opening of the "C" is directed to the rearward direction of the internal combustion engine. Lubricating oil lubricates the front main bearing insert, the main journal, the crank shaft and the crank shaft cap.
Accordingly, a front end cavity is defined by the flange shaft, the seal means, the oil seal case, the crank shaft cap, the cylinder block and the main journal.
Therefore, even if the lubricating oil leaks into the front end cavity, the seal means prevents the lubricating oil from leaking out from the cylinder block.
During the compression strokes and expansion strokes of the internal combustion engine, blow-by gas leaks from between contacting portions of a cylinder wall of a cylinder block and piston rings which are secured to a piston. Normally the blow-by gas includes a large amount of water. Because the front end cavity is almost sealed by the flange shaft, the seal means, the oil seal case, the crank shaft cap, the cylinder block and the main journal, the blow-by gas which leaks into the front end cavity stays within the front end cavity. As a result, the outer peripheral surface of the flange shaft rusts from the water included in the blow-by gas. The rust on the outer peripheral surface detracts from the sealing effect between the seal means and the flange shaft.
In a similar manner, blow-by gas stays in a rear end cavity and an outer peripheral surface of a flange shaft rusts from the water in the blow-by gas.